Flow rate control system and shower plate used for partial pressure control system

ABSTRACT

A partial pressure control system  45  includes two valves  2  which are branched from an operation gas supply pipe  44  and which variably control operation gas, pressure sensors  3  which are respectively connected to the each valves  2  in series and which detect pressure of the operation gas, and a controller  25  which proportionally controls the operation of the valves  2  based on detection result of the pressure sensors  3 , thereby relatively controlling pressures P 1  and P 2  of the two valves. With this configuration, it is possible to reduce wastefull consumption of the operation gas, and to enhance the responsivity with respect to change of setting and the like.

BACKGROUND OF THE INVENTION

The present invention relates to a partial pressure control system, aflow rate control system, which outputs operation gas at a predeterminedpartial pressure ratio, and a shower plate used for the partial pressurecontrol system.

DESCRIPTION OF THE RELATED ART

A flow rate control system which supplies operation gas to a wafercontrols a flow rate of operation gas which is to be supplied to acenter area and an edge area of the wafer to uniformly supply theoperation gas to the wafer. FIG. 6 is a schematic block diagram of aconventional flow rate control system 100. FIGS. 7 and 8 are plan viewsof conventional shower plates 122 (122A, 122B).

In a flow rate control system 100, flow rate control devices 101A, 101B,101C and 101D are respectively connected to gas supply sources for gassuch as O₂, Ar, C₄F₈ or CO. The flow rate control devices 101A to 101Dinclude flow rate control valves 102A, 102B, 102C, 102D and flowmeters103A, 103B, 103C, 103D, respectively, and adjust openings of the flowrate control valves 102A to 102D based on flow rates detected by theflowmeters 103A to 103D.

The flow rate control devices 101A to 101D are connected to a partialflow control device 110 through an operation gas supply pipe 104, andsupply operation gas to an etching device 120. In the flow rate controldevice 110, flow rate control valves 111A and 111B are connected to theoperation gas supply pipe 104 in parallel, and flowmeters 112A and 112Bare the flow rate control valves 111A and 111B in series. The flow ratecontrol valves 111A and 111B and the flowmeters 112A and 112B areconnected to a controller 113. The controller 113 controls the flow ratecontrol valves 111A and 111B based on flow rates detected by theflowmeters 112A and 112B. The flow rate control valves 111A and 111B ofthe partial flow control device 110 are respectively connected to acenter shower 125 and an edge shower 126 of the shower plate 122incorporated in the etching device 120.

The shower plate 122 is disposed above a lower electrode 121 which heatsa wafer W. As shown in FIGS. 7 and 8, the shower plate 122(122A,122B) isprovided with a large number of gas holes 123 in its surface opposed tothe wafer W. A perfectly circular partition wall ring 124 is mounted onthe shower plate 122(122A,122B), thereby dividing the shower plate 122into a circular center shower 125 and an annular edge shower 126. In theshower plate 122A shown in FIG. 7, the gas holes 123A are arranged intoa square shape, and they are arranged in a form of a square from acenter to a periphery of the wafer W. In the shower plate 122B shown inFIG. 8, gas holes 123B are arranged concentrically, and are arrangeconcentrically from a center to a periphery of the wafer W.

Thus, in the flow rate control system 100, if a flow rate control valve102B of a flow rate control device 101B is opened, Ar is branched intothe flow rate control valves 111A and 111B of the partial flow controldevice 110 from the operation gas supply pipe 104, and supplied onto thewafer W from the center shower 125 and the edge shower 126. At thattime, the partial flow control device 110 controls the opening andclosing operation of the flow rate control valves 111A and 111B based onthe flow rates detected by the flowmeters 112A and 112B, and Ar isinjected at the predetermined flow rate using the center shower 125 andthe edge shower 126. Therefore, Ar can uniformly be supplied to theentire wafer W (for example, paragraphs 0032, 0037, 0039 and FIGS. 1, 5,7 and 8 of Japanese Patent Laid-open Publication No. 10-121253).

According to the conventional flow rate control system 100, however,responsivity with respect to the change of settings is inferior, andoperation gas can not uniformly be supplied to the wafer W in somecases.

In generally, in the flow rate control system 100, the partial flowcontrol device 110 is provided on the side of the etching device 120,and the gas supply source and the flow rate control devices 101A to 101Dare provided on the side of a gas box away from the etching device 120.Thus, the wiring volume of the operation gas supply pipe 104 is great.The partial flow control device 110 controls the flow rate controlvalves 111A and 111B based on flow rates which are output from theflowmeters 112A and 112B and thus, it takes time to control them. Thus,in the flow rate control system 100, when the flow rate of operation gasis changed by the flow rate control devices 101A to 101D, it takes timeuntil the flow rate of the operation gas flowing through the operationgas supply pipe 104 is stabilized, and since it takes time for thepartial flow control device 110 to control, the responsivity of changeof settings is inferior. On the other hand, the etching processing iscarried out within a short time for preventing the chemical reaction ofthe operation gas. Thus, the flow rate control system 100 can not finishthe control operation gas until the etching processing is completed, andcan not uniformly supply the operation gas to the wafer W in some cases.

To enhance the responsivity, it seems better idea to control thepressure of the operation gas injected from the center shower 125 andthe edge shower 126 using an absolute value instead of using the flowrate control device 110. However, such a system for controlling thepressure of the operation gas using the absolute value, it is necessaryto provide a large tank on the primary sides of the flow rate controlvalves 111A and 111B and to store the operation gas using the pressurecorresponding to the absolute value, and there is a problem thatoperation gas is squandered. In addition, according to the system forcontrolling the pressure of the operation gas using the absolute value,the responsivity with respect to the change of settings is inferior. Forexample, when it is necessary to change the pressure ratio of operationgas which is to be output from the flow rate control valves 111A and111B, the pressure of operation gas to be stored in the large tank mustbe changed, and it takes time to control. When it is necessary to changethe kind of operation gas, since the flow rate of the operation gas tobe supplied from the operation gas supply pipe 104 to the partial flowcontrol device 110 is varied depending upon the characteristics of theoperation gas, it is difficult to swiftly determine the flow rate ofoperation gas which is to be output from the flow rate control valves111A and 111B.

The layout of the gas holes 123 on the shower plate 122 also one ofreasons why the operation gas can not be supplied to the wafer Wuniformly. That is, when the gas holes 123A are arranged in the form ofsquare as shown in FIG. 7, since distances between adjacent gas holes123A are constant, the discharging density of the operation gas shouldbe constant theoretically, but the probability that the gas holes 123Aare crashed when the partition wall ring 124 is mounted is high. Thatis, as shown in FIG. 9, although the partition wall ring 124A does notcrush the gas holes 123A, the partition wall rings 124B, 124C and 124Dcrush one or some of the gas holes 123A. If the gas holes 123A arecrushed, the hole areas of the gas holes 123A are varied, and thedischarging density of the operation gas can not be equalized. If thepartition wall ring 124 is mounted such that the gas holes 123A are notcrushed, the shape of the partition wall ring 124 is deformed, and itbecomes difficult to mount the partition wall ring 124 on the showerplate 122A. If the gas hole 123B are arranged concentrically as shown inFIG. 8, it becomes easy to mount the partition wall ring 124 such thatthe gas hole 123B are not crushed. However, distances between the gashole 123B on the shower plate 122B are varied, and there is a problemthat the discharging density of the operation gas can not be equalized.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a partialpressure control system capable of reduce wastefull consumption ofoperation gas, and capable of enhancing the responsivity with respect tothe change of settings. It is a second object of the invention toprovide a flow rate control system having excellent responsivity andcapable of outputting operation gas at a precise partial pressure ratio.It is a third object of the invention to provide a shower plate used forthe partial pressure control system capable of equalizing thedischarging density of operation gas on a subject of supply.

To achieve the first object, the present invention provides a partialpressure control system comprising: a plurality of pressure controlunits which are branched from an operation gas supply pipe forcontrolling pressure of operation gas, variably; pressure detectingunits which are connected the pressure control units in series fordetecting the pressure of the operation gas; and a control unit whichproportionally controls operation of the pressure control units based ondetection result of the pressure detecting units and which relativelycontrols output pressures of the plurality of pressure control units.

The control unit may specify one of the pressure control units as acontrol subject, and the control unit may control only the specifiedpressure control unit, thereby keeping a pressure ratio.

The control unit may specify one of the pressure control units as thecontrol unit based on a pressure ratio which is input to the partialpressure control system.

The number of the pressure control units may be two, the control unitmay specify one of the two pressure control units as the control subjectdepending upon whether the pressure ratio which is input to the partialpressure control system is greater than 1 or not.

When the pressure ratio which is input to the partial pressure controlsystem is obtained by dividing pressure in a first pressure control unitby pressure in a second pressure control unit, a target pressure of thefirst pressure control unit is expressed as a product of the pressureratio and the pressure of the second pressure control unit, a targetpressure of the second pressure control unit is expressed as a quotientobtained by dividing the pressure in the first pressure control unit bythe pressure ratio, when the pressure ratio is smaller than 1, only thetarget pressure in the first pressure control unit is controlled, andwhen the pressure ratio is equal to or greater than 1, only the targetpressure of the second pressure control unit is controlled.

The control unit may specify one of the pressure control units as thecontrol subject based on the detection result of the pressure detectingunit.

The partial pressure control system may further comprise a zero pointconfirming unit, all of the pressure control units are fully opened, andwhen supply of the operation gas is stopped, the zero point confirmingunit confirms whether pressure detected by the pressure detecting unitis within tolerance with respect to a zero point.

To achieve the second object, the present invention provides a flow ratecontrol system comprising: a flow rate control device including a flowrate control valve connected to a gas supply source, and a flow ratedetecting unit which detects a flow rate output by the flow rate controlvalve, the flow rate control device controlling the flow rate controlvalve based on a detection result of the flow rate detecting unit; anoperation gas supply pipe connected to the flow rate control device; anda partial pressure control system including a plurality of pressurecontrol units which are branched from the operation gas supply pipe andwhich control pressure of operation gas, variably, pressure detectingunits which are respectively connected to the pressure control units inseries and which detects pressure of the operation gas, and a controlunit which proportionally controls operation of the pressure controlunit based on detection result of the pressure detecting unit and whichrelatively controls output pressure of the pressure control units.

The flow rate control system may further comprise a zero pointconfirming unit, all of the pressure control units are fully opened, andwhen supply of the operation gas is stopped, the zero point confirmingunit confirms whether pressure detected by the pressure detecting unitis within tolerance with respect to a zero point.

To achieve the third object, the present invention also provides ashower plate used for a partial pressure control system in which theshower plate is partitioned by a partition wall member and divided intoa plurality of areas, the areas are connected to the partial pressurecontrol system, and operation gas injected from each area to the supplysubject is controlled. Adjacent gas holes for injecting the operationgas are arranged in a form of a regular triangle, and are arranged in aform of hexagon from a center to a periphery with respect to the supplysubject.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a partial pressure control system accordingto a first embodiment of the present invention;

FIG. 2 is a schematic block diagram of a flow rate control systemaccording to the first embodiment of the invention;

FIG. 3 shows one example of zero point confirmation according to thefirst embodiment, wherein a vertical axis shows pressure and a lateralaxis shows time;

FIG. 4 is a plan view of a shower plate according to a second embodimentof the invention;

FIG. 5 shows an example of a disposition of a partition wall memberaccording to the second embodiment of the invention;

FIG. 6 is a schematic block diagram of a conventional flow rate controlsystem;

FIG. 7 is a plan view of a conventional shower plate;

FIG. 8 is a plan view of another conventional shower plate; and

FIG. 9 shows an example of a disposition of a partition wall member in ashower plate in which gas holes are arranged in a form of square.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The action of the embodiments will be explained. Operation gas suppliedfrom a gas supply source is supplied to an operation gas supply pipesimultaneously when a flow rate control valve of a flow rate controldevice is opened. At that time, the flow rate control device detects aflow rate which is output from the flow rate control valve by means ofthe flow rate detecting unit, the flow rate control valve is controlledbased on the detection result, thereby supplying the operation gas atthe predetermined flow rate to the operation gas supply pipe.

The operation gas is output such that the operation gas is branched intopressure control units of the partial pressure control system from theoperation gas supply pipe. The partial pressure control system detectsthe output pressure of the pressure control unit by means of a pressuredetecting unit, and proportionally controls the pressure control unitbased on the detection result of the pressure detecting unit. Since thepressure control unit of the partial pressure control system isconnected to the operation gas supply pipe in a branched manner, if oneof pressure control unit is proportionally controlled to vary the outputpressure, output pressure of the other pressure control unit is alsovaried relatively. Thus, the partial pressure control system can outputthe operation gas from the pressure control unit at the predeterminedpartial pressure ratio irrespective of a flow rate of operation gassupplied from the operation gas supply pipe.

Even if the flow rate control system is disposed in such a manner thatthe flow rate control device and the partial pressure control system areseparated away from each other and a piping volume of the operation gassupply pipe becomes large and the setting of the flow rate of theoperation gas is changed by the flow rate control device, the partialpressure control system proportionally controls the pressure controlunit based on the pressure detected by the pressure detecting unit andoutputs operation gas at the predetermined partial pressure ratioirrespective of the flow rate of the operation gas supplied from theoperation gas supply pipe. Therefore, the controlling time is shortened.

According to the flow rate control system of the present invention, theresponsivity with respect to change of settings is excellent, andoperation gas can be output at a precise partial pressure ratio.

Since the partial pressure control system controls operation gas underrelative pressure based on pressure which is output from the pressurecontrol unit, it is unnecessary to provide a large tank on the primaryside of the pressure control unit to store the operation gas unlike acase where the operation gas is controlled under absolute pressure. Tochange the pressure ratio of operation gas which is output from eachpressure control unit, it is only necessary for the partial pressurecontrol system to control the pressure control unit. Also when the kindsof operation gas is to be changed, since the partial pressure controlsystem controls the operation gas under the absolute pressure, it ispossible to swiftly determine the pressure ratio of the operation gaswhich is output from each pressure control unit irrespective of kinds ofoperation gas. Therefore, according to the partial pressure controlsystem, it is possible to reduce the wastefull consumption of operationgas, and to enhance the responsivity with respect to the change ofsettings.

When operation gas is to be controlled in a partial pressure manner, ifone of the pressure control units having the least output pressure isspecified as a subject to be controlled, the plurality of pressurecontrol units can be controlled in a diversion manner.

The partial pressure control system and the flow rate control systeminclude a zero point confirming unit, and confirm whether the controlstate is constant or not.

When the supply of operation gas is stopped in a state in which all ofthe pressure control units are fully opened, operation gas remaining inthe operation gas supply pipe passes through the pressure control unitand flows downstream and at the same time, the pressure to be detectedby each pressure detecting unit is also reduced toward the zero point.The zero point confirming unit confirms the zero point position based onthe reduction of the pressure. With this, the flow rate control systemand the partial pressure control system can swiftly find a trouble ofthe system.

Next, the action of the shower plate used for the partial pressurecontrol system will be explained.

In the shower plate used for the partial pressure control system, areasdivided by the partition wall member are connected to the partialpressure control system, and pressures of operation gases which areoutput the respective areas are controlled. Since the gas holes fromwhich the operation gases are injected are arranged in the form oftriangle in the shower plate, the distances between the adjacent gasholes are substantially constant. Since the gas holes are arranged in aform of hexagon from a center toward a periphery with respect to thesupply subject, when the shower plate is divided by a perfectly circularpartition wall member for example, the gas holes are less prone to becrushed. Therefore, the probability of crush of the gas holes by thepartition wall member is lowered, and the discharging density of theoperation gas can be uniform on the supply subject.

Next, the first embodiment of the shower plate used for the partialpressure control system, the flow rate control system and the partialpressure control system of the present invention will be explained withreference to the drawings. FIG. 2 is a schematic block diagram of a flowrate control system 50A.

The flow rate control system 50A in FIG. 2 is used for etchingprocessing of a semiconductor producing apparatus. The flow rate controlsystem 50A has a gas supply source for gas such as O₂, Ar, C₄F₈ or CO,and a plurality of flow rate control devices 41A, 41B, 41C and 41Dconnected to the gas supply source. The flow rate control devices 41A to41D includes flow rate control valves 42A, 42B, 42C and 42D andflowmeters (corresponding to “flow rate detecting unit”) 43A, 43B, 43Cand 43D, and adjust the openings of the flow rate control valves 42A to42D based on flow rates detected by the flowmeters 43A to 43D.

The operation gases supplied from the flow rate control devices 41A to41D are injected from a shower plate 52 of a chamber 51 through anoperation gas supply pipe 44 and a partial pressure control system 45.At that time, in order to supply the operation gas to the center shower53 and the edge shower 54 of the shower plate 52 at a predeterminedpartial pressure ratio, the partial pressure control system 45 controlsthe operation gas.

The partial pressure control system 45 includes a pressure controldevice 1A connected to the center shower 53, and a pressure controldevice 1B connected to the edge shower 54. The pressure control devices1A and 1B includes a pressure control valve (corresponding to “pressurecontrol units”, and if one of them is defined as a first pressurecontrol unit, the other one can be defined as a second pressure controlunit) 2, and a pressure sensor (corresponding to “pressure detectingunit”) 3, and they are respectively connected to controllers(corresponding to “control device” of the partial pressure controlsystem 45) 25 so that one of outputs is adjusted based on the detectionresult of the pressure sensor 3. A central controller (including onescorresponding to “control device” of the flow rate control system 50A)46 for controlling the operation of the entire semiconductor producingapparatus is connected to the controller 25. The central controller 46always monitors the flow rate control state of the operation gas.

FIG. 1 is a block diagram of the partial pressure control system 45.

The controller 25 of the partial pressure control system 45 areconnected to valve controllers 9 incorporated in the pressure controldevices 1A and 1B, and adjusts the openings of the normally-openedvalves 8. With this adjustment, pressures of operation gases which areoutput by the pressure control units comprising the valve controllers 9and the valves 8 are controlled. A piezo-valve or the like may be usedas the valve 8.

The controller 25 includes a Central Processing Unit (it is called a CPUin the following description) 26, fully opens one of the valves 8 havinghigher output pressure, specifies the other valve 8 having lower outputpressure as a control subject, and controls the pressure ratio. The CPU26 includes a control subject determining section 27 which determines acontrol subject in accordance with pressure ratio command K (here,K=target pressure P1/target pressure P2) which is input to a deviceoperation screen of the central controller 46. Connected to the controlsubject determining section 27 in parallel are a calculating section 28which calculates the target pressure P2 (=P1/K) of the pressure controldevice 1B based on the pressure ratio command K, and a calculatingsection 34 which calculates the target pressure P1 (=K×P2) of thepressure control device 1A based on the pressure ratio command K.

A control section 30 is connected to the calculating section 28. Thecontrol section 30 determines a control signal based on a deviationbetween the pressure P2 which is fed back from the pressure sensor 3 ofthe pressure control device 1B and the target pressure P2 (=P1/K) of thepressure control device 1B which is input from the calculating section28. The control section 30 is connected to the valve controller 9 of thepressure control device 1B through a D/A converter 32. The pressuresensor 3 of the pressure control device 1B is connected to thecalculating section 34 through an A/D converter 33, and is feedbackconnected to an upstream of the control section 30.

A control section 36 is connected to the calculating section 34. Thecontrol section 36 determines a control signal based on a deviationbetween a pressure P1 which is fed back from the pressure sensor 3 ofthe pressure control device 1A and the target pressure P1 (=KP2) of thepressure control device 1A which is input from the calculating section34. The control section 36 is connected to the valve controller 9 of thepressure control device 1A through the D/A converter 38. The pressuresensor 3 of the pressure control device 1A is connected to thecalculating section 28 through the A/D converter 39, and is feedbackconnected to the upstream of the control section 36.

The partial pressure control system 45 is operated as follows.

That is, in the flow rate control system 50A shown in FIG. 2, when theflow rate control valves 42A to 42D of the flow rate control devices 41Ato 41 D are closed and no operation gas is supplied, a cut-signal isinput to the CPU 26 of the controller 25 as shown in FIG. 1. The CPU 26receives the cut-signal, and stops the operation of the valvecontrollers 9 of the pressure control devices 1A and 1B through the D/Aconverters 32 and 38. Therefore, no control signal is supplied to thevalves 8 of the pressure control devices 1A and 1B, and the valves 8 arefully (normally) opened.

Next, a case where Ar is supplied to the wafer W in the flow ratecontrol system 50A shown in FIG. 2 will be explained. A pressure ratiocommand K is input to the flow rate control system 50A from the deviceoperation screen of the central controller 46. When the process istransferred, the flow rate control system 50A controls Ar in accordancewith a parameter in a recipe setting screen.

If the flow rate control valve 42B of the flow rate control device 41Bis opened, Ar supplied from the gas supply source is supplied to theoperation gas supply pipe 44 simultaneously. At that time, the flow ratecontrol device 41B detects the flow rate of the Ar which is output fromthe flow rate control device 41B by the flowmeter 43B, and controls theflow rate control device 41B based on the detection result, therebysupplying Ar to the operation gas supply pipe 44 at the predeterminedflow rate.

The Ar is supplied to the wafer W from the shower plate 52 through theoperation gas supply pipe 44 and the partial pressure control system 45.That is, in the partial pressure control system 45, since the valves 8of the pressure control devices 1A and 1B are fully opened, pressures ofthe Ar passing through the pressure sensors 3 of the pressure controldevices 1A and 1B are increased to substantially the same level, the Aris branched from the operation gas supply pipe 44 into the valves 8 ofthe pressure control devices 1A and 1B, and is supplied to the wafer Wthrough the center shower 53 and the edge shower 54 of the shower plate52.

At that time, the pressure sensor 3 of the pressure control device 1Adetects the pressure P1 of the Ar which is output from the valve 8, andoutputs a detection signal to the calculating section 28 of the CPU 26through the A/D converter 39, and the detection signal is fed back tothe control section 36.

The pressure sensor 3 of the pressure control device 1B detects thepressure P2 of the Ar which is output from the valve 8, outputs adetection signal to the calculating section 34 of the CPU 26 through theA/D converter 33, and the detection signal is fed back to the controlsection 30.

The CPU26 receives an arbitrary pressure ratio command K (here, K=targetpressure P1/target pressure P2), and judges whether the pressure ratiocommand K is smaller than 1. If the pressure ratio command K is smallerthan 1, i.e., the target pressure P2 of the pressure control device 1Bis greater than the target pressure P1 of the pressure control device1A, the CPU 26 judges that the valve 8 of the pressure control device 1Ais the control subject, and immediately starts controlling the valve 8of the pressure control device 1A. At that time, since the valve 8 ofthe pressure control device 1B is fully opened, the pressure P2 of thepressure control device 1B is increased. The CPU 26 monitors thepressure P2 of the pressure control device 1B and controls the valve 8of the pressure control device 1A such that the pressure ratio becomesequal to the instruction value. That is, the control section 36 of theCPU 26 determines the control signal with respect to the valve 8 of thepressure control device 1A such that the pressure P1 of the pressurecontrol device 1A and the pressure P2 of the pressure control device 1Bbecome equal to the partial pressure ratio based on the deviationbetween the target pressure P1 (=KP2) of the pressure control device 1Aand the pressure P1 which is fed back from the pressure sensor 3 of thepressure control device 1A. In accordance with this control, in thepressure control device 1A, the valve controller 9 adjusts the openingof the valve 8. Thus, the Ar is output to the wafer W at thepredetermined partial pressure ratio from the center shower 53 and theedge shower 54 and is supplied to the entire wafer W uniformly.

If the pressure ratio command K is not smaller than 1, i.e., thepressure P1 of the pressure control device 1A is equal to or greaterthan the pressure P2 of the pressure control device 1B, the valve 8 ofthe pressure control device 1B is controlled in the same manner as thatdescribed above so that the pressure P2 of the pressure control device1B is allowed to instantaneously reach the target value. Thus, the Arcan be supplied to the center area and the edge area of the wafer W atthe predetermined partial pressure ratio. In this case, a value (P1/K)obtained by dividing the pressure P1 detected by the pressure sensor 3of the pressure control device 1A by the pressure ratio command K isused as the target pressure P2 of the pressure control device 1B in thecalculating section 28.

Next, a case in which the flow rate control system 50A changes the flowrate of operation gas will be explained. In general, in the flow ratecontrol system 50A, the gas supply source and the flow rate controldevice 41 are provided on the side of a gas box located away from thechamber 51, and the partial pressure control system 45 is provided onthe side of the chamber 51. Therefore, the piping volume of theoperation gas supply pipe 44 becomes large in size. In such a flow ratecontrol system 50A, when the opening of the flow rate control valve 42Bof the flow rate control device 41B is changed and the flow rate ofoperation gas to be supplied to the operation gas supply pipe 44 ischanged, the partial pressure control system 45 proportionally controlsthe valves 8 of the pressure control devices 1A and 1B based on thepressures P1 and P2 detected by the pressure sensors 3 of the pressurecontrol devices 1A and 1B irrespective of the flow rate of Ar suppliedfrom the operation gas supply pipe 44, and outputs the Ar at thepredetermined partial pressure ratio. Therefore, the control time isshortened. Thus, the responsivity of the flow rate control system 50Awith respect to the change of settings is excellent, and it is possibleto output the operation gas at a precise partial pressure ratio.

In the partial pressure control system 45, since the Ar is controlledunder the relative pressure based on the pressures P1 and P2 which areoutput by the valves 8 of the pressure control devices 1A and 1B, it isunnecessary to provide large tanks on the primary sides of the valves 8of the pressure control devices 1A and 1B to store the Ar unlike a casein which the operation gas is controlled under the absolute pressure. Inthe partial pressure control system 45, when the pressure ratio of Arwhich is output from the valves 8 of the pressure control devices 1A and1B, it is only necessary to control smaller one of the pressures P1 andP2 of the valves 8 of the pressure control devices 1A and 1B.

Next, a case in which the flow rate control system 50A changes the kindsof operation gas will be explained.

When the flow rate control system 50A changes the kinds of operation gas(e.g., from Ar to CO in this embodiment), the flow rate control valve42B of the flow rate control device 41B is closed, and the energizationto the valve controllers 9 of the pressure control devices 1A and 1B isstopped, and the valves 8 is fully opened. With this operation, Arremaining downstream of the flow rate control devices 41A to 41D isdischarged into the chamber 51 from the pressure control devices 1A and1B. Then, the flow rate control valve 42D of the flow rate controldevice 41 D is opened to supply CO to the partial pressure controlsystem 45 from the operation gas supply pipe 44, and the CO is injectedfrom the center shower 53 and the edge shower 54 of the shower plate 52at the predetermined partial pressure ratio.

In the partial pressure control system 45, the pressure sensors 3 detectpressures P1 and P2 of CO which are output from the valves 8 of thepressure control devices 1A and 1B, and the CO is controlled under therelative pressure based on the detection results. Therefore, even if thecharacteristics such as compression ratio of the CO and Ar are differentfrom each other, the partial pressure control system 45 can swiftlydetermines the pressure ratio of CO which is to be output from thevalves 8 of the pressure control devices 1A and 1B.

Thus, according to the flow rate control system 50A of the embodiment,the flow rate control system of this embodiment comprises the flow ratecontrol devices 41A to 41D which control the flow rate control valves42A to 42D based on the detection results of the flowmeters 43A to 43D.The flow rate control devices 41A to 41D include the flow rate controlvalves 42A to 42D connected to the gas supply source, and the flowmeters43A to 43D which detect the flow rates which are output from the flowrate control valves 42A to 42D. The flow rate control system 50A alsocomprises the operation gas supply pipe 44 connected to the flow ratecontrol devices 41A to 41D, and the partial pressure control system 45includes the two valves 8 which are branched from the operation gassupply pipe 44 and which variably control the operation gas, thepressure sensors 3 which are respectively connected to the valves 8 inseries for detecting the pressures P1 and P2 of the operation gas, andthe controller 25 which proportionally controls the operation of thevalves 8 based on the detection result of the pressure sensors 3 torelatively control the pressures P1 and P2 which are output from the twovalves 8. Therefore, the responsivity with respect to the change ofsetting is excellent, and it is possible to output the operation gas ata precise partial pressure ratio.

The partial pressure control system 45 of this embodiment comprises thetwo valves 8 which are branched from the operation gas supply pipe 44and which variably control the operation gas, the pressure sensors 3which are connected to the valves 8 in series and which detect thepressures P1 and P2 of the operation gases, and the controller 25 whichproportionally controls the operations of the valves 8 based on thedetection results of the pressure sensors 3 to relatively control thepressures P1 and P2 of the two valves 8. Therefore, it is possible toreduce the wastefull consumption of operation gas, and to enhance theresponsivity with respect to the change of settings.

In the partial pressure control system 45 of this embodiment, thecontroller 25 specifies, as the control subject, smaller one of thepressures P1 and P2 of the valves 8 of the pressure control devices 1Aand 1B, and controls the action of the control subject based on thedetection result of the pressure sensor 3. Therefore, it is possible tocontrol the valves 8 of the pressure control devices 1A and 1B in adiversion manner.

At that time, when the partial pressure control system 45 controls thepressure P1 to be output from the pressure control device 1A, thepartial pressure control system 45 calculates the target pressure P1(=K×P2) of the pressure control device 1A from the pressure P2 detectedby the pressure control device 1B and the pressure ratio command K, andcontrols the opening and closing operation of the valve 8 of thepressure control device 1A. On the other hand, when the partial pressurecontrol system 45 controls the pressure P2 to be output from thepressure control device 1B, the partial pressure control system 45calculates the target pressure P2 (=P1/K) of the pressure control device1B from the pressure P1 detected by the pressure control device 1A andthe pressure ratio command K, and controls the opening and closingoperation of the valve 8 of the pressure control device 1B. Thus, it ispossible to shorten the control time of the valves 8, and to enhance theprocessing ability of the entire system.

The partial pressure control system 45 and the flow rate control system50A, which control the partial pressure include a zero point confirmingunit in the controller 25, and confirm whether the control state isconstant. When the control of the partial pressure of operation gas isto be stopped or when the kinds of operation gas are to be changed, thezero point confirming unit is allowed to operate to detect theabnormality of the partial pressure control system 45.

The zero point confirming unit may be operated when the flow ratecontrol devices 41A to 41D are to be closed. As shown in FIG. 3, thezero point confirming unit close the flow rate control devices 41A to 41D to stop the supply of operation gas, and when the pressures P1 and P2detected by the pressure sensor 3 become equal to or smaller thanpredetermined threshold value D, the zero point confirming unit confirmsa zero point shift based on the pressure reduction of the pressuresensor 3.

More specifically, if the control of the valves 8 by the valvecontrollers 9 of the pressure control devices 1A and 1B is stopped andthe flow rate control devices 41A to 41D are closed, operation gasremaining downstream of the flow rate control devices 41A to 41D issupplied into the chamber 51 from the valves 8 of the pressure controldevices 1A and 1B. With this, the pressures P1 and P2 detected by thepressure sensors 3 are reduced toward the zero point.

When one of the pressures P1 and P2 of the valves 8 becomes equal to orlower than the predetermined threshold value D, pressures P1 and P2 ofthe valves 8 are detected at constant intervals (e.g., 500 ms msecintervals) by the pressure sensor 3, and it is judged whether thedetected pressures P1 and P2 are within tolerance. For example, thepressure difference (P1-P2) between the pressures P1 and P2 iscalculated, and it is judged whether the pressure difference is withintolerance C (within 0.1 kPa) with respect to the zero point, and whithereach of the pressures P1 and P2 of the valves 8 is smaller than apredetermined threshold value B (e.g., −0.15 kPa). There, the toleranceC is a deviation amount of the zero point position which can notfunctionally be permitted, and the threshold value B is a value whichshould not be shown by the pressure sensor 3 under a normal condition.

If it is judged that the pressure P1 and P2 difference is not withintolerance C, or when it is judged that any one of the output pressuresP1 and P2 is smaller than the predetermined threshold value B, it isjudged that the output pressures P1 and P2 are not within tolerance C.In this case, the pressure which should be indicated under a normalcondition is not indicated, abnormality is detected. If the detection ofabnormality is continuously counted several times (three times in thisembodiment), an alarm is given to inform an operator of the abnormalityof the partial pressure control system 45. The reason why it isnecessary to count the detection of abnormality several times is toprevent an erroneous detection. With this, the flow rate control system50A and the partial pressure control system 45 can swiftly find a systemtrouble.

A second embodiment of the shower plate used for the partial pressurecontrol system, the flow rate control system and the partial pressurecontrol system will be explained. FIG. 4 is a plan view of a showerplate 80. FIG. 5 shows an example of layout of a partition wall ring 83.

The shower plate 80 shown in FIG. 4 is provided in the chamber 51 likethe shower plate 52 of the first embodiment, and is used for supplyingoperation gas to the center area and the edge area of the wafer(corresponding to “supply subject”) W at a predetermined partialpressure ratio. The shower plate 80 is of a disk-like shape, and theshower plate 80 is divided into a disk-like center shower 81 and anannular edge shower 82 by mounting a perfectly circular partition wallring (corresponding to “partition wall member”) 83 on the shower plate80. A plurality of gas holes 84 injecting the operation gas are formedin a surface of the shower plate 80 opposed to the wafer W. The adjacentgas holes 84 are arranged in a form of regular triangle, and arearranged in a form of hexagon from center to periphery with respect tothe wafer W.

The shower plate 80 supplies operation gas which is controlled by thepartial pressure control system to the wafer W from the gas holes 84 ofthe center shower 81 and the edge shower 82. Since the gas holes 84 ofthe shower plate 80 are arranged in the form of regular triangle,distances between the adjacent gas holes 84 are constant. Since the gasholes 84 are arranged in the form of hexagon from center to peripherywith respect to the wafer W, the gas holes 84 are not prone to becrushed when the shower plate 80 is divided by the partition wall ring83. That is, when the partition wall ring 83 is mounted as shown in FIG.5, although the partition wall ring 83D crushes the gas holes 84, thepartition wall rings 83A, 83B and 83C do not crush the gas holes 84.Thus, the probability that the gas holes 84 are crushed in the case ofthe shower plate 80 when the perfectly circular partition wall ring 83is mounted is remarkably low as compared with the shower plate 122A (seeFIG. 9) in which the gas holes 123A are arranged in a form of square. Itis easy to mount the partition wall rings 83.

The shower plate 80 used for the partial pressure control system of thisembodiment is concentrically partitioned by the partition wall ring 83and divided into a plurality of areas, and the pressure of operation gassupplied to the wafer W from each area is controlled by the partialpressure control system, the adjacent gas holes 84 injecting theoperation gas are arranged in the form of regular triangle, and arearranged in the form of hexagon from the center to the periphery withrespect to the wafer W. Thus, the probability that the gas holes 84 arecrushed by the partition wall ring 83, and the discharging density ofoperation gas can be equalized on the wafer W.

Although the embodiments of the present invention have been explainedabove, the invention is not limited to the embodiments, and variousapplications can be made.

(1) For example, in the above embodiment, the pressure of operation gaswhich is output from the two valves 8 is adjusted to the pressure ratiocommand K. Alternatively, the partial pressure of operation gas which isoutput from three or more valves 8 may be adjusted.

(2) For example, valves 8 are controlled such that the valves 8 arefully opened when the control is started, one of the valves 8 havinggreater output pressure is left opened and the other valve 8 havingsmaller output pressure is specified as the control subject in the firstembodiment. Alternatively, the valves 8 may be fully closed when thecontrol is started, and the valves 8 of the pressure control devices 1Aand 1B may be controlled.

(3) For example, the partial pressure control system 45 is used for theflow rate control system 50A which is used for a semiconductor producingapparatus in the first embodiment. However, if the purpose is to outputoperation gas at a predetermined partial pressure ratio, the subject towhich the invention is applied is not limited to the semiconductorproducing apparatus.

Effect of the Invention will be explained

The partial pressure control system of the present invention includes aplurality of pressure control units which are branched from an operationgas supply pipe and which variably control pressure of operation gas,pressure detecting units which are respectively connected to thepressure control units in series and which detect pressure of operationgas, and a control unit which proportionally controls operation of thepressure control unit based on a detection result of the pressuredetecting unit, thereby relatively controlling the pressures of thepressure control units. Therefore, it is possible to reduce wastefullconsumption of the operation gas, and to enhance the responsivity withrespect to change of setting and the like.

The flow rate control system of the present invention comprises, a flowrate control device including a flow rate control valve connected to agas supply source, and a flow rate detecting unit which detects a flowrate output by the flow rate control valve, the flow rate control devicecontrolling the flow rate control valve based on a detection result ofthe flow rate detecting unit, an operation gas supply pipe connected tothe flow rate control device, and a partial pressure control systemincluding a plurality of pressure control units which are branched fromthe operation gas supply pipe and which variably control pressure ofoperation gas, pressure detecting units which are respectively connectedto the pressure control units in series and which detects pressure ofthe operation gas, and a control unit which proportionally controlsoperation of the pressure control unit based on detection result of thepressure detecting unit and which relatively controls output pressure ofthe pressure control units. Therefore, the responsivity with respect tothe change of settings and the like is excellent, and it is possible tooutput operation gas at a precise partial pressure ratio.

In the shower plate of the present invention used for a partial pressurecontrol system, the shower plate is partitioned by a partition wallmember and divided into a plurality of areas, the areas are connected tothe partial pressure control system, and operation gas injected fromeach area to the supply subject is controlled. Adjacent gas holes forinjecting the operation gas are arranged in a form of a regulartriangle, and are arranged in a form of hexagon from a center to aperiphery with respect to the supply subject. Therefore, the probabilitythat the gas holes are crushed by the partition wall member can belower, and discharging density of the operation gas can be equalized onthe supply subject.

1-7. (canceled)
 8. A flow rate control system comprising: a flow ratecontrol device including a flow rate control valve connected to a gassupply source, and a flow rate detecting unit which detects a flow rateoutput by the flow rate control valve, the flow rate control devicecontrolling the flow rate control valve based on a detection result ofthe flow rate detecting unit; an operation gas supply pipe connected tothe flow rate control device; and a partial pressure control systemincluding a plurality of pressure control units which are branched fromthe operation gas supply pipe and which control pressure of operationgas, pressure detecting units which are respectively connected to theeach pressure control units in series and which detects pressure of theoperation gas, and a control unit which proportionally controlsoperation of the pressure control unit based on detection result of thepressure detecting unit and which relatively controls output pressure ofthe pressure control units.
 9. The flow rate control system according toclaim 8, wherein the control unit specifies one of the pressure controlunits as a control subject, and the control unit controls only thespecified pressure control unit, thereby keeping a pressure ratio. 10.The flow rate control system according to claim 9, wherein the controlunit specifies one of the pressure control units as the control unitbased on a pressure ratio which is input to the partial pressure controlsystem.
 11. The flow rate control system according to claim 10, whereinthe number of the pressure control units is two, the control unitspecifies one of the two pressure control units as the control subjectdepending upon whether the pressure ratio which is input to the partialpressure control system is greater than 1 or not.
 12. The flow ratecontrol system according to claim 11, wherein when the pressure ratiowhich is input to the partial pressure control system is obtained bydividing pressure in a first pressure control unit by pressure in asecond pressure control unit, a target pressure of the first pressurecontrol unit is expressed as a product of the pressure ratio and thepressure of the second pressure control unit, a target pressure of thesecond pressure control unit is expressed as a quotient obtained bydividing the pressure in the first pressure control unit by the pressureratio, when the pressure ratio is smaller than 1, only the targetpressure in the first pressure control unit is controlled, and when thepressure ratio is equal to or greater than 1, only the target pressureof the second pressure control unit is controlled.
 13. The flow ratecontrol system according to claim 9, wherein the control unit specifiesone of the pressure control units as the control subject based on thedetection result of the pressure detecting unit.
 14. The flow ratecontrol system according to claim 8, further comprising a zero pointconfirming unit, wherein all of the pressure control units are fullyopened, and when supply of the operation gas is stopped, the zero pointconfirming unit confirms whether pressure detected by the pressuredetecting unit is within tolerance with respect to a zero point.
 15. Ashower plate which is formed into a disk-like shape for injectingoperation gas to a supply subject, wherein adjacent gas holes forinjecting the operation gas are arranged in a form of substantiallyregular triangle, and the gas holes are arranged in a form of hexagonfrom a center to a periphery of the shower plate corresponding to thesupply subject.
 16. The shower plate according to claim 15, wherein theshower plate is used for a partial pressure control system whichcomprises a partial pressure control system including a plurality ofpressure control units which are branched from the operation gas supplypipe and which control pressure of operation gas, pressure detectingunits which are respectively connected to the pressure control units inseries and which detects pressure of the operation gas, and a controlunit which proportionally controls operation of the pressure controlunit based on detection result of the pressure detecting unit and whichrelatively controls output pressure of the pressure control units. 17.The shower plate according to claim 16, wherein the shower plate ispartitioned by a perfectly circular partition wall member and dividedinto a plurality of areas, the areas are respectively connected to thepressure control units of the partial pressure control system.